FIG. 8 illustrates an example of a power seat sliding device for sliding a seat forwards and backwards by a motor.
In the figure, a lower rail 1 is provided with a threaded rod 3 disposed in a longitudinal direction using a bracket 4 in a state where the threaded rod 3 is prevented from rotation.
A gearbox 5 is disposed on an upper rail 7 using a bracket 6. In the gearbox 5, a nut member is rotatably disposed. The nut member has an inner peripheral surface in which a female thread is formed and threadably engaged with the threaded rod 3. In the gearbox 5, a worm is also disposed. The worm can be rotatively driven by a motor. Further, the outer periphery of the nut member forms a worm wheel with which the worm is threadably engaged.
In this structure, when the motor runs, the nut member is rotated via the worm in the gearbox 5. The threaded rod 3, which is threadably engaged with the nut member, is prevented from rotation. Thus, the upper rail 7 moves relative to the lower rail 1.
As illustrated in FIG. 9, the gearbox 5 includes a first parallel face (lower face in this FIG. 5b parallel to an output shaft 5a, a second parallel face (upper face in this FIG. 5c parallel to the first parallel face 5b, a first orthogonal face (front face in this FIG. 5d orthogonal to the output shaft 5a, and a second orthogonal face (rear face in this FIG. 5e parallel to the first orthogonal face 5d. 
The bracket 6 configured to mount the gearbox 5 on the upper rail 7 is formed by bending a plate member. The bracket 6 includes a base part 6a, a first bent part 6b, a second bent part 6c, a first mounting part 6d, and a second mounting part 6e. The base part 6a supports the first parallel face 5b of the gearbox 5. The first bent part 6b is bent from the base part 6a, which is on the side of the first orthogonal face 5d of the gearbox 5, faces the first orthogonal face 5d of the gearbox 5, and extends toward the upper rail 1. The first bent part 6b has a hole 6f through which a threaded rod penetrates. The second bent part 6c is bent from the base part 6a on the side of the second orthogonal face 5e of the gearbox 5, and extends toward the upper rail 1 along the second orthogonal face 5e of the gearbox 5. The second bent part 6c has a hole 6g through which a threaded rod penetrates. The first mounting part 6d is bent from the end of the first bent part 6b in a direction away from the first orthogonal face 5d of the gearbox 5 in parallel with the base part 6a. The first mounting part 6d is attached to the upper rail 1. The second mounting part 6e is bent from the end of the second bent part 6c in a direction away from the second orthogonal face 5e of the gearbox 5 in parallel with the base part 6a. The second mounting part 6e is attached to the upper rail 1 (see, for example, Patent Document 1).